The independent effects of gravity and inertia on running mechanics

2000 ◽  
Vol 203 (2) ◽  
pp. 229-238 ◽  
Author(s):  
Y.H. Chang ◽  
H.W. Huang ◽  
C.M. Hamerski ◽  
R. Kram
Keyword(s):  
Inertial Force ◽  
Normal Weight ◽  
Inertial Forces ◽  
Step Cycle ◽  
Resultant Vector ◽  
Normal Mass ◽  
Reaction Forces ◽  
Independent Effects ◽  
Experimental Treatments ◽  
Running Mechanics

It is difficult to distinguish the independent effects of gravity from those of inertia on a running animal. Simply adding mass proportionally changes both the weight (gravitational force) and mass (inertial force) of the animal. We measured ground reaction forces for eight male humans running normally at 3 m s(−)(1) and under three experimental treatments: added gravitational and inertial forces, added inertial forces and reduced gravitational forces. Subjects ran at 110, 120 and 130 % of normal weight and mass, at 110, 120 and 130 % of normal mass while maintaining 100 % normal weight, and at 25, 50 and 75 % of normal weight while maintaining 100 % normal mass. The peak active vertical forces generated changed with weight, but did not change with mass. Surprisingly, horizontal impulses changed substantially more with weight than with mass. Gravity exerted a greater influence than inertia on both vertical and horizontal forces generated against the ground during running. Subjects changed vertical and horizontal forces proportionately at corresponding times in the step cycle to maintain the orientation of the resultant vector despite a nearly threefold change in magnitude across treatments. Maintaining the orientation of the resultant vector during periods of high force generation aligns the vector with the leg to minimize muscle forces.

Tip-Over Stability Analysis for a Wheeled Mobile Manipulator

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Shuai Guo ◽  
Tao Song ◽  
Fengfeng (Jeff) Xi ◽  
Richard Phillip Mohamed
Keyword(s):  
Stability Analysis ◽  
Path Planning ◽  
Static Load ◽  
System Stability ◽  
Mobile Manipulator ◽  
Inertial Forces ◽  
Horizontal Position ◽  
Reaction Forces ◽  
Simulation Results

A method is presented for tip-over stability analysis of a wheeled mobile manipulator. A wheeled mobile manipulator may tip over resulting from its operation. In this study, first a Newton–Euler formulation is applied to formulate the manipulator’s reaction forces and moments exerted onto the mobile platform. Tip-over criterion is derived to judge the system stability. Three load and motion analyses are carried on. The first static load deals with links and payload to show the effect of the horizontal position of the system’s center of gravity (CG). The second and third are the inertial forces resulting from joint speeds and accelerations, respectively. Case study is path planning with tip-over criterion result which can make the system stable along the path. The simulation results demonstrate the effectiveness of the proposed method.

Mechanisms of Gait Adaptation in Overweight Pregnant Women

2020 ◽  
Vol 110 (4) ◽  
Author(s):  
Jolanta Pauk ◽  
Dagna Swinarska ◽  
Kristina Daunoraviciene
Keyword(s):  
Pregnant Women ◽  
Plantar Pressure ◽  
Normal Weight ◽  
Ground Reaction Forces ◽  
Third Trimester ◽  
Gait Adaptation ◽  
The Third ◽  
Plantar Pressure Distribution ◽  
Gait Parameters ◽  
Reaction Forces

Background Pregnancy is a period when a woman's body undergoes changes. The purpose of this study was to analyze the mechanisms of gait adaptation in overweight pregnant women regarding spatiotemporal gait parameters, ground reaction forces, and plantar pressure distribution. Methods The tests were performed in 29 normal-weight pregnant women and 26 pregnant women who were overweight before pregnancy. The measurements included spatiotemporal gait parameters, in-shoe plantar pressure distribution, and ground reaction forces during gestation. Results The results indicate that both normal-weight and overweight pregnant women make use of the same spatiotemporal gait parameters to increase body stability and safety of movement during pregnancy. The double-step duration in the third trimester of pregnancy was higher in normal-weight and overweight pregnant women compared with in the first trimester (P < .05). A significant change in pressure amplitude was found under all anatomical parts of the foot in the third trimester (P < .05). The results also suggest a higher increase in the maximum amplitude of force in overweight pregnant women in the third trimester compared with the normal-weight group. Conclusions This study suggests that both normal-weight and overweight pregnant women use different mechanisms of gait adaptation during pregnancy. In practice, understanding the biomechanical changes in women's gait can protect the musculoskeletal system during gestation.

scholarly journals Effects of Velocity and Weight Support on Ground Reaction Forces and Metabolic Power during Running

2008 ◽  
Vol 24 (3) ◽  
pp. 288-297 ◽  
Author(s):  
Alena M. Grabowski ◽  
Rodger Kram
Keyword(s):  
Body Weight ◽  
Normal Weight ◽  
Treadmill Running ◽  
Ground Reaction Forces ◽  
Metabolic Power ◽  
Data Set ◽  
Weight Support ◽  
Scientific Goal ◽  
Reaction Forces ◽  
Support Body Weight

The biomechanical and metabolic demands of human running are distinctly affected by velocity and body weight. As runners increase velocity, ground reaction forces (GRF) increase, which may increase the risk of an overuse injury, and more metabolic power is required to produce greater rates of muscular force generation. Running with weight support attenuates GRFs, but demands less metabolic power than normal weight running. We used a recently developed device (G-trainer) that uses positive air pressure around the lower body to support body weight during treadmill running. Our scientific goal was to quantify the separate and combined effects of running velocity and weight support on GRFs and metabolic power. After obtaining this basic data set, we identified velocity and weight support combinations that resulted in different peak GRFs, yet demanded the same metabolic power. Ideal combinations of velocity and weight could potentially reduce biomechanical risks by attenuating peak GRFs while maintaining aerobic and neuromuscular benefits. Indeed, we found many combinations that decreased peak vertical GRFs yet demanded the same metabolic power as running slower at normal weight. This approach of manipulating velocity and weight during running may prove effective as a training and/or rehabilitation strategy.

scholarly journals An unrecognized inertial force induced by flow curvature in microfluidics

2021 ◽  
Vol 118 (29) ◽  
pp. e2103822118
Author(s):  
Siddhansh Agarwal ◽  
Fan Kiat Chan ◽  
Bhargav Rallabandi ◽  
Mattia Gazzola ◽  
Sascha Hilgenfeldt
Keyword(s):  
Entire Range ◽  
State Of The Art ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Inertial Force ◽  
Inertial Forces ◽  
Inertial Effects ◽  
Inviscid Flows ◽  
Flow Curvature ◽  
Complete Set

Modern inertial microfluidics routinely employs oscillatory flows around localized solid features or microbubbles for controlled, specific manipulation of particles, droplets, and cells. It is shown that theories of inertial effects that have been state of the art for decades miss major contributions and strongly underestimate forces on small suspended objects in a range of practically relevant conditions. An analytical approach is presented that derives a complete set of inertial forces and quantifies them in closed form as easy-to-use equations of motion, spanning the entire range from viscous to inviscid flows. The theory predicts additional attractive contributions toward oscillating boundaries, even for density-matched particles, a previously unexplained experimental observation. The accuracy of the theory is demonstrated against full-scale, three-dimensional direct numerical simulations throughout its range.

Effects of Gait Variations on Grip Force Coordination During Object Transport

2008 ◽  
Vol 100 (5) ◽  
pp. 2477-2485 ◽  
Author(s):  
Priska Gysin ◽  
Terry R. Kaminski ◽  
Chris J. Hass ◽  
Cécile E. Grobet ◽  
Andrew M. Gordon
Keyword(s):  
Grip Force ◽  
Gait Cycle ◽  
Time Window ◽  
Inertial Force ◽  
Step Length ◽  
Support Surface ◽  
Inertial Forces ◽  
Force Coupling ◽  
Temporal Coupling ◽  
Object Transport

In object transport during unimpeded locomotion, grip force is precisely timed and scaled to the regularly paced sinusoidal inertial force fluctuations. However, it is unknown whether this coupling is due to moment-to-moment predictions of upcoming inertial forces or a longer, generalized time estimate of regularly paced inertial forces generated during the normal gait cycle. Eight subjects transported a grip instrument during five walking conditions, four of which altered the gait cycle. The variations included changes in step length (taking a longer or shorter step) or stepping on and over a stable (predictable) or unstable (unpredictable support surface) obstacle within a series of baseline steps, which resulted in altered frequencies and magnitudes of the inertial forces exerted on the transported object. Except when stepping on the unstable obstacle, a tight temporal coupling between the grip and inertial forces was maintained across gait variations. Precision of this timing varied slightly within the time window for anticipatory grip force control possibly due to increased attention demands related to some of the step alterations. Furthermore, subjects anticipated variations in inertial force when the gait cycle was altered with increases or decreases in grip force, relative to the level of the inertial force peaks. Overall the maintenance of force coupling and scaling across predictable walking conditions suggests that the CNS is able to anticipate changes in inertial forces generated by gait variations and to efficiently predict the grip force needed to maintain object stability on a moment-to-moment basis.

Electromagnetic radiation and inertial forces

2019 ◽  
Vol 32 (4) ◽  
pp. 480-483
Author(s):  
Nasko Elektronov ◽  
Zhivko Kushev
Keyword(s):  
Electromagnetic Radiation ◽  
Doppler Effect ◽  
Inertial Force ◽  
Spectral Shift ◽  
Inertial Forces ◽  
Spectral Shifts ◽  
Nearby Stars ◽  
The Doppler Effect

The influence of the Coriolis inertial force generated by the orbital and spin motions of distant objects on the electromagnetic radiation energies during the exchange of photons between such objects has been considered. A red or blue spectral shift occurrence in a passive observation mode that is not associated with the Doppler effect or other known effects has also been shown. The relations found are used to calculate the spectral shifts for several nearby stars from our galaxy, as well as the spectral shifts of several galaxies. The results are close to the values currently observed.

Insulin and Weight Status in Adolescents: Independent Effects of Intensity of Physical Activity and Peak Aerobic Power

2008 ◽  
Vol 20 (1) ◽  
pp. 29-39 ◽  
Author(s):  
Daniela A. Rubin ◽  
Robert G. McMurray ◽  
Joanne S. Harrell
Keyword(s):  
Physical Activity ◽  
Weight Status ◽  
Aerobic Power ◽  
Vigorous Physical Activity ◽  
Normal Weight ◽  
Habitual Physical Activity ◽  
Fat Free Mass ◽  
Fasting Insulin ◽  
Overweight Adolescents ◽  
Independent Effects

Differences in insulin concentrations between normal weight or overweight adolescents (n = 437) were determined depending on their habitual physical activity (PA) and aerobic power (pVO2max). Tertiles were computed for PA (survey) and pVO2max (submaximal predicted cycle test). Independent of their weight, adolescents in the upper 2 tertiles for vigorous PA had lower insulin concentrations than those in the bottom tertile (p < .05). Adolescents in the top tertile for pVO2max expressed per kg fat-free mass also had lower insulin concentrations than those in the medium and bottom tertiles (p = .002). In youth, vigorous physical activity and aerobic power are associated with fasting insulin independent of weight status.

Kinematics and Kinetics of 2 Styles of Partial Forward Lunge

2008 ◽  
Vol 17 (4) ◽  
pp. 387-398 ◽  
Author(s):  
Daniel J. Wilson ◽  
Kyle Gibson ◽  
Gerald L. Masterson
Keyword(s):  
Inertial Forces ◽  
Shear Forces ◽  
Inverse Dynamic ◽  
Kinematic Data ◽  
Anterior Translation ◽  
Research Institution ◽  
Reaction Forces ◽  
Analysis Laboratory ◽  
Kinetics Of ◽  
Kinematics And Kinetics

Objective:To evaluate the anterior shift of the body’s center of gravity (CG) and the associated inertial forces produced by 2 styles of a partial forward lunge.Setting:Gait-analysis laboratory of a research institution.Participants:10 healthy volunteers.Intervention:3 trials of each lunge.Main Outcome Measures:Kinematic data were collected, and inertial reaction forces were resolved into net compressive and shear forces using an inverse dynamic model.Results:Significantly (P < .001) greater anterior translation of the CG was found with an arms-in-front v arms-across-chest lunge style. No significant differences were found between the average peak inertial compressive and shear forces of the 2 styles (427 ± 184 N v 426 ± 187 N, −536 ± 113 N v −538 ± 127 N).Conclusion:Anterior translation of the CG was larger with the arms-forward partial-lunge position, creating increased balance demands. Both styles produced clinically safe (posteriorly directed) inertial shear forces, with greater anterior CG shift with the arms-forward style.

Reaction Force Analysis in Generalized Machine Systems

1973 ◽  
Vol 95 (2) ◽  
pp. 617-623 ◽  
Author(s):  
D. A. Smith
Keyword(s):  
Dynamic Systems ◽  
Virtual Work ◽  
Reaction Force ◽  
Inertial Forces ◽  
Force Analysis ◽  
Lagrange’S Equation ◽  
Reaction Forces ◽  
Applied Forces ◽  
Machine Systems ◽  
Centers Of Mass

A method is developed which reduces the calculation of reaction forces for multi-degree-of-freedom, constrained, mechanical, dynamic systems to a process of accumulating a sum of terms representing inertial forces, applied forces, and Lagrange multiplier forces. This method results in an approach to reaction force calculations which is computationally more efficient than either virtual work or equilibrium when these methods are applied in conventional ways. The method is based on selecting a tree for the network being simulated in which the chords of the network correspond to revolute pairs (for two-dimensional systems). When such a tree is determined, Lagrange’s equation with constraint is used to represent the mechanical system. If the paths to the centers of mass and the paths associated with applied forces are developed from tree branches, the Lagrange multipliers are directly interpretable in terms of the total reaction forces at the chords of the network. These multipliers are obtained in the process of determining the system motion. The remaining reaction forces and torques are determined by a sequence of additions.

The Effects of Cycling on Running Mechanics

1996 ◽  
Vol 12 (4) ◽  
pp. 470-479 ◽  
Author(s):  
Edward J. Quigley ◽  
James G. Richards
Keyword(s):  
High Speed ◽  
Reaction Force ◽  
Vertical Displacement ◽  
Ankle Joints ◽  
Angular Velocities ◽  
Reaction Forces ◽  
Stance Time ◽  
Left And Right ◽  
Force Data ◽  
Running Mechanics

This study investigated the mechanical effects that cycling has on running style which may explain the discomfort associated with the transition from cycling to running. The joint angles, angular velocities, reaction forces, and reaction moments of the left and right hip, knee, and ankle joints as well as stance time, flight time, stride length, and maximum vertical displacement of the center of gravity were measured using high-speed video and ground reaction force data. Data were collected from 11 competitive biathletes and triathletes. Each subject's running mechanics were determined from 10 trials for each of three conditions: (a) unfatigued, (b) immediately following 30 min of running, and (c) immediately following 30 min of bicycling. The results indicate that a person's running mechanics, as described by the variables above, are virtually unchanged between each of the three conditions. Therefore, awkwardness of the bicycle-to-run transition may not be related to a change in running mechanics.

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